Optical device and imaging device with mechanism for reducing condensation

1. An optical device comprising: a lens assembly comprising: at least one lens having an optical axis for receiving light from an object located at a first side of the optical axis; and a holder for holding the at least one lens; a circuit board for performing at least one process based on the received light; and a housing having an opening and configured to house the lens assembly and the circuit board therein, the lens assembly being exposed to an outside of the housing via the opening, wherein: the holder comprises: a wall portion provided to intersect with a direction of the optical axis; and a holding body having an upper wall and mounted to the wall portion, the holding body being configured to surround at least part of the at least one lens; the wall portion extends upward with respect to the upper wall of the holding body; at least part of the upper wall of the holding body is exposed via the opening; and the wall portion and the upper wall of the holding body are configured to guide air, entering an inside of the housing via the opening, to change a direction of the air so as not to be directed toward the circuit board.

2. The optical device according to claim 1 , wherein: the wall portion has a surface; the holding body has a substantially tubular shape, and one tubular end mounted to the surface of the wall portion; and an area of the surface of the wall portion is larger than a cross-sectional area of the tubular end of the holding body.

3. The optical device according to claim 2 , wherein: the upper wall of the holding body is configured to guide the air, entering into the inside of the housing via the opening, to be directed toward the surface of the wall portion; and the surface of the wall portion is configured to guide the air guided by the upper wall of the holding body so as not to be directed toward the circuit board.